1. Field of the Invention
The present invention relates to a safety apparatus for a fuel tank in a vehicle or the like, which can prevent outflow of flammable liquid, e.g., gasoline, light oil or the like which is stored in the fuel tank, caused by an accident such as a vehicle collision, rollover or the like.
2. Discussion of the Background
Conventionally, a fire prevention apparatus of a tank for a flammable fuel is known, such as a kind of safety apparatus for a fuel tank, as shown in Japanese Patent Application Kokoku (Post-Exam) Publication No. Sho 61-28529.
The fire prevention apparatus described in this publication comprises an impact sensing mechanism for sensing the impact caused by a crash of the vehicle to output a detection signal, a gelling agent tank for storing a gelling agent which can gelatinize a flammable liquid, and a forcing mechanism for forcing the gelling agent in the gelling agent tank into the fuel tank according to the detection signal of the impact sensing mechanism.
The fire prevention apparatus for the fuel tank having the above-described structure forces a flammable fluid in the gelling agent tank into the fuel tank when the vehicle crashes.
U.S. Pat. No. 3,876,011 discloses a safety apparatus for extinguishing fires in vehicles. The fire prevention apparatus described in this publication comprises a mechanical impact sensing mechanism for sensing the impact caused by a crash of the vehicle, an extinguishing agent tank for storing an extinguishing agent which can extinguish a fire, and a mechanical forcing mechanism for forcing the extinguishing agent into the fuel tank by using a valve which is opened by the force of the impact.
Each of the fire prevention apparatuses described in the references uses an acceleration sensing mechanism for sensing an impact caused by a vehicle crash. Although such acceleration sensors can detect the crash of the vehicle, than cannot detect whether the fuel tank is largely damaged by the impact given to the fuel tank, or not. Consequently, according to conventional fire prevention apparatuses for the fuel tank, there is a serious problem in that the gelling or extinguishing agent may be supplied into the fuel tank even though no emergency is occurring to the fuel tank.
U.S. Pat. No. 4,633,967 discloses a safety apparatus for extinguishing fires in vehicles. The fire prevention apparatus described in this publication comprises a mechanical impact sensing mechanism for sensing the impact in only the horizontal directions received by the fuel tank of the vehicle, an extinguishing agent tank for storing an extinguishing agent which can extinguish a fire, and a mechanical supplying mechanism for supplying the extinguishing agent into the fuel tank by using a valve which is mechanically opened by the force of the impact.
However, the reference does not disclose a method which can prevent a fire by gelatinizing the fuel in the fuel tank by forcing a gelling agent into the fuel tank. The fire prevention apparatus shown in the reference can detect the impact in only the four horizontal directions; however, it cannot detect the impact in the two vertical directions. Such an impact in one of the vertical directions is a serious matter with respect to the fire prevention in a vehicle because impacts in the vertical directions often cause fire or an explosion following extensive damage suck as a crack to the fuel tank. For example, when the vehicle runs onto the sidewalk, when a tire is released from the vehicle, after a crash, or when the fuel tank is extensively damaged by some projection, or the like.
There sometimes are various signs indicating danger of a vehicle collision, before a serious accident such as a collision actually occurs. It has been desired to provide an apparatus for previously detecting such signs to prevent occurrence of accidents, as soon as possible.